Impulse-actuated lock-in relaying system



Dec. 12, 1933. L 1,939,071

IIPULSE-ACTUATED LOCK-IN RELAYING SYSTEM Filgd Feb. 1. 1933 l Circa/7f II I I I I'I I I Scum of Siyna/ impulses. 9

WITNESSES: INVENTOR ATTORNEY Patented Dec. 12, 1933 PATENT OFFICEIMPULSE-ACTUATED LOCK-IN RELAYING SYSTEM Thomas H. Long, Irwin,

Pa., assignor to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a corporation of Pennsylvania Application February 1,1933. Serial No. 654,644

12 Claims.

My invention has particular relation to the problem of securing arelaying action, or other control-circuit operation, in response to asignal impulse of shorter duration than has been utilizable for controlpurposes prior to my invention. In sorting applications, where alight-responsive device is utilized to scan an object or objects for thepurpose of sorting, or for the purpose of detecting discolorationstherein, it is desirable to speed up the process as much as possible,but prior to my invention, this speeding-up process was limited by thefact that if the signal were ,too brief, it would not lock-in (includingthe thought of locking-out) a relaying circuit so as to make possiblethe operation of some control device therefrom. The shortest duration ofsignal which could thus be utilized, prior to my inention, was of theorder of micro-seconds.

The principal object of my invention is to devise some practical meansfor utilizing an electrical signal of very brief duration, preferably ofthe order of a few micro-seconds, or even less. I am not limited to anyparticular application of my relaying system, as in sortingapplications, but the same may be utilized in rapid counters, or toprevent chattering which would result from other relaying devices,particularly devices of the so-called balance type, or for otherpurposes.

A more particular object of my invention is to provide a relaying systemof the class described, utilizing what is sometimes known as a flatvapor-arc rectifier, or an evacuating are device comprising two spacedmain electrodes in an evacuated tank, with a make-alive electrode incontinuous contact with oneofthe main electrodes, forming a cathode spoton the latter when the make-alive electrode is suitably energized, as bypassing a few amperes of direct current therethrough from the make-aliveelectrode to the main electrode on which the cathode spot is to beformed. Such a make-alive electrode may be a resistance rod, such as amolded carborundum material having clay binder or other binder whichdoes not emit gases under operating conditions, or other poorlyconducting material which is not destroyed under the operatingconditions. The particular effect of such a makealive means is thatthere is no arc, or other source of electron-emission, in the tankduring the period when there is no are playing between the mainelectrodes, so that, after the current-flow in the main-arc circuit isinterrupted, the main arc will not restrike until the make-aliveelectrode is suitably energised.

With the foregoing and other objects in view, my invention consists inthe apparatus and systems hereinafter described and claimed andillustrated in the accompanying drawing, the single figure of which is adiagrammatic view of circuits and apparatus embodying my invention in apreferred form.

As shown in the drawing, my relay system utilizes a source of signalimpulses, by which I mean a source for supplying an electrical signal ofextremely brief duration, preferably of the order of a few micro-secondsor even less. The signal may be any change in current or voltage, notusually involving a complete cessation of current or voltage in thesignal circuit at any time.

For example, if the signal circuit comes from" the amplifying equipmentof a scanner utilizing a light beam, its voltage normally will be, say,1000 volts, which may be reduced to 900 volts for a brief moment of timeduring the signal impulse, when the scanning light beam flashes over adiscoloration on the object scanned. The signal circuit is indicated onthe drawing by the numeral 1.

For responding to the signal impulses, I utilize a control means 2having a control circuit 3, which is responsive to the signal, and amain circuit 4. The control means 2 is shown as a three-electrodeamplifier tube having an anode 5, a grid 6, and a hot cathode 7, theanode and the cathode being disposed in the main circuit, while thecontrol circuit is connected to the grid and to the cathode. The grid 6is connected to the cathode '7 by means of a grid-leak circuitcomprising a grid-leak resistor 8 and sometimes also a small biasingbattery 9 for reducing the current normally flowing through the grid.The grid 6, with its grid-leak circuit, is coupled to the source ofsignal impulses through a coupling capacitor 11 in such a way that theexpected, change in the signal-circuit conditions, which constitutes thesignal, causes current to flow through the capacitor 11 momentarily inthe direction from the grid to the signal circuit, as indicated by thesigns and in the drawing.

The main circuit 4 also includes, in series relation therein, an arcingdevice,'such as the flat rectifier 12 which was referred to in theopening paragraphs of this specification. The drawing shows thisrectifier diagrammatically as comprising a main anode 13, a cathode 14of mercury or other vaporizable reconstructing material, and amake-alive electrode 15. The main circuit 4 is normally completed bymeans of an are passing from the main anode 13 to the cathode 14.

The main circuit 4 also includes a control device or relay 16 forperforming the useful function which is required of the relaying system.As shown, the control device 16 is represented as a relay elementcomprising an actuating coil 17, which is in series circuit relationwith the main circuit 4, and one or more movable contact devices 18 and19. The first contact device 18 may close first, upon the deenergizationof the relay, (the relay being normally energized), and may thus beutilized to energize any desired controlled circuit 21, as indicated.

The main circuit 4 is completed by a high-voltage battery 22 whichsupplies direct current passing through the relay coil 1'], the fiatrectifier 1314 and the amplifier tube 2, returning from the cathode '7of the latter to the negative terminal of the battery 22.

In operation, the grid 6 of the amplifier tube is normally not active,carrying only a few milliamperes, and permitting the amplifier to carryits normal plate-circuit current, which flows through the main circuitincluding the fiat rectifier 12 and the relay coil 1'7. In general, thefiat rectifier, being an arcing device, requires a sufiicient current,perhaps of the order of at least one-fourth of an ampere, in order tomaintain the arc and hold the relay 16 in its normal actuated condition.

The source of signal impulses is so designed, with detectors andamplifiers, that the signal impulse consists of a sudden drop in thevoltage applied to the coupling capacitor 11. For example, thesignal-source side of the coupling capacitor may suddenly be made 100volts more negative than it was before the signal came in. Current willimmediately flow through the grid-leak resistor 8, thus imposing on thegrid 6 a voltage which is usually not a great deal less than the signalvoltage, say, volts, for example. This voltage is sufiicient tointerrupt the fiow of platecircuit current through the tube 2, thus alsointerrupting the arc current in the fiat rectifier 12, causing thecathode spot in the latter to disappear.

It will be noted that the fiat rectifier 12 may be any arcing devicecomprising two spaced stationary main. electrodes 13 and 14, one ofwhich is always non-electron-emitting and the other one of which emitselectrons from its cathode spot when an arc is playing from it to themain anode, but at no other times. It is not essential that theelectrode on which the cathode spot appears shall be of a specialcathode material,' as a cathode spot may be formed on any conductor, soas to initiate the arc. It is essential, however, that the space betweenthe two main electrodes 13 and 14 shall be subjected to such strongdeionizing influence that an arc will not restrike between saidelectrodes even though voltage is re-applied thereto, after aninterruption of the arc, with only a moment's delay, such as 3 or 4micro-seconds, or even less than 1 micro-second. Such strong deionizinginfluence may include anything which will quickly deionize the spacebetween the main electrodes, so that the breakdown voltage between theelectrodes quickly assumes a sufficiently high value to preventrestriking immediately after the main arc goes out at any time. A veryeffective deionizing influence of this sort is a good vacuum, such as isordinarily provided in mercury-arc rectifiers.

therein, and in utilizing a make-alive which is dead during thenon-arcing periods, rather than utilizing a keep-alive which is arcing,and thus supplying ions and electrons to main arcing space, all duringthe'non-arcing period, as in the type of mercury-arc rectifier thathasheretofore been the usual type.

At the same time that the arc is extinguished I in the fiat rectifier12, as a result of the blocking f or interruption of the main-circuitcurrent l through the amplifier tube 2, the exciting current isinterrupted in the relay 16, thus causing this relay to drop its movablecontacts 18 and 19.

The principal contacts 18 are shown as closing a circuit 21 for doingthe useful work which should be done in response to the signal impulse.The

other movable contacts 19 of the relay are auxiliary contacts which mayor may not be utilized,

being shown as energizing the make-alive 15 of the fiat rectifier, fromany suitable source such as the battery 24. These auxiliary contacts 19may either close simultaneously with the main 1 contacts 18, or,preferably, may close slightly later. Assuming that the high negativepotential on the grid 6 has meanwhile disappeared, the 1 main arc in thefiat rectifier 12 will practically instantaneously start, as soon as themake-alive electrode 15 is suitably energized from the makealive battery24,- and a current will thus be reapplied to the energizing coil 1'7 ofthe relay, causing the latter to begin to pickup its contacts 18 and 19,there being a sufficient sluggishness in this action to enable thecontrolled circuit 21 to perform its intended useful function.

In order to prevent the application of an extremely high voltage acrossthe main electrodes of the fiat rectifier while the current iscollapsing, or becoming zero, in the highly inductive actuating coil 17of the relay, after an interruption of the main arc circuit, it is verydesirable to utilize a small capacitor 25 connected across the relaycoil 17 to prevent the presence ot such a high voltage. Otherwise, thehigh voltage induced in the inductive circuit 1'7 might persist longerthan the duration of the signal impulse, and longer than the duration ofthe high negative bias on the grid 6, thus causing the main arc torestrike prematurely, if the induced voltage was higher than thebreak-down voltage which could be withstood by the arc space of the fiatrectifier at the moment.

In connection with the coupling capacitor 11 in the grid circuit of theamplifier tube 2, it is preferable that the time constant of thiscapacitor and the grid-leak resistor 8 shall be at least as long as theminimum expectable duration of signal to which the relay system isadapted to respond, and preferably the time constant should be from 10to times said duration of signal. Thus, this time constant is the timeduring which current will fiow, from the hot-cathode conductor and thegrid-leak resistor 8, to the coupling capacitor 11, for the purpose ofre-adjusting the capacitor-charge to the voltage conditionsexisting inthe signal circuit while the signal impulse is being received. While thecoupling capacitor 11 is thus charging, or readjusting its charge, thegrid 6 gradually becomes less negative, until, at the end of the timeconstant, it would be restored a large part of the way back to itsnormal, non-blocking potential. It is thus necessary for the timeconstant of the capacitor-resistor circuit 118 to be sumciently high toinsure that the grid 6 shall not return to its non-blocking potentialwithin the expected duration of the brief signal impulse.

While I have shown my invention in but a single preferred application,and in but a single form of embodiment, it will be obvious that manychanges may be made by those skilled in the art, without departing fromthe essential thought and spirit of my invention. I desire, therefore,that the appended claims shall be accorded the broadest constructionconsistent with their language and the prior art.

I claim as my invention: i

1. A relay system for obtaining a lock-in response from an electricalsignal of very brief duration, comprising a control means having acontrol circuit and a main circuit so related that said control circuitis adapted to respond instantaneously to said signal to momentarilyinterrupt the current-flow in said main circuit, said main circuitcomprising, in series relation therein, an arcing device comprising twospaced main electrodes between which an arc plays to carry the currentnormally flowing in said main circuit, said spaced electrodes beingsubjected to such strong deionizing influence that an arc will notrestrike therebetween even though the currentflow is interrupted onlymomentarily by said control means, a source of current supply for saidmain circuit, and a control device responsive to the current-flow insaid maincircuit.

2. A relay system' for obtaining a lock-in response from an electricalsignal of very brief duration, comprising a control means having acontrol circuit and a main circuit so related that said control circuitis adapted to respond instantaneously to said signal to momentarilyinterrupt the current-flow in said main circuit, said main circuitcomprising, in series relation therein, an arcing device comprising twospaced main electrodes between which an arc plays to carry the currentnormally flowing in said main circuit, said spaced electrodes beingsubjected to such strong deionizing influence that an arc will notrestrike therebetween even though the currentflow is interrupted onlymomentarily by said control means, a source of current supply for saidmain circuit, an electromagnetic relay having an actuating windingenergized from said main circuit, and acapacitor shunting said actuatingwinding.

3. A relay system-for obtaining a lock-in response from an electricalsignal as brief as a' few micro-seconds, or less, in duration,comprising a control tube having a control circuit and a main circuit sorelated that said control circuit is adapted to respond instantaneouslyto said signal to momentarily interrupt the current-flow in said maincircuit, said main circuit comprising, in series relation therein, anevacuated arcing device comprising two spaced main electrodes betweenwhich an arc plays to carry the current normally flowing in said maincircuit, a source of current supply for said main circuit, and a controldevice responsive to the current-flow in said main circuit, saidevacuated arcing device being of a type which will not restrike its arewhen its voltage is restored after a brief interruption for the durationof the signal.

4. A relay system for obtaining a lockin response from an electricalsignal as brief as a few micro-seconds, or less, in duration, comprisinga control tube having a control circuit and a main circuit so relatedthat said control circuit is adapted to respond instantaneously to saidsignal to momentarily interrupt the current-flow in said main circuit,said main circuit comprising, in series relation therein, an evacuatedarcing de- -vice comprising two spaced main electrodes be-' 5. A relaysystem for obtaining a lock-in response from an electrical signal asbrief as a few micro-seconds, or less, in duration, compris ing acontrol tube having a control circuit and a main circuit so related thatsaid control circuit is adapted to respond instantaneously to saidsignal to momentarily interrupt the currentflow in said main circuit,said main circuit comprising, in series relation therein, an evacuatedarcing device comprising two spaced stationary main electrodes betweenwhich an arc plays to carry the current normally flowing in said maincircuit, said main electrodes comprising one electrode which is alwayssubstantially non-electronemitting and another electrode which ceasesemitting electrodes substantially instantaneously upon an interruptionof the arc, a source of current supply for said main circuit, and acontrol device responsive to the current-flow in said main circuit.

6. A relay system for obtaining a lock-in response from an electricalsignal as brief as a few micro-seconds or less, in duration, comprisinga control tube having a control circuit anda main circuit so relatedthat said control circuit is adapted to respond instantaneously to saidsignal to momentarily interrupt the current-flow in said main circuit,said main circuit comprising, in series relation therein, an evacuatedarcing device comprising two spaced stationary main electrodes betweenwhich an arcplays to carry the current normally flowing in said maincircuit, said main electrodes comprising a main anode and a vaporizablereconstructing cathode, enclosed in an evacuated tank containing noother source of electron emission when the main-electrode arc isextinguished, asource of current sup-- ply for said main circuit, and acontrol device responsive to the current-flow in said main circuit.

7. A relay system for obtaining a lock-in response from an electricalsignal as brief as a few micro-seconds, or less, in duration, comprisinga control tube having a cathode, a grid and an anode, a grid-leakcircuit between the grid and the cathode and including a grid-leakresistance, and a capacitor for coupling the grid to the incomingelectrial signal in such a manner that the grid becomes stronglynegative for the duration of the signal, the time constant of thecapacitor and the grid-leak resistance being longer than the minimumexpectable duration of signal to which the relay system is adapted torespond, 9. main circuit serially including said anode and said .cathodeas apart thereof, said control tube being adapted to respondinstantaneously to the incoming electrical signal to substantially blockthe current-flow in said main circuit for substantially the duration ofsaid signal, said main circuit comprising, in series relation therein,an arcing device comprising two spaced main electrodes, between which anarc plays to carry the current normallyflowing in said main circuit,said spaced electrodes being subjected to such strong deionizinginfluence that an arc will not restrike therebetween even though thecurrentflow is interrupted only for the minimum expectable duration ofsignal to which the relay system is adapted to respond by said controltube, a source of direct-current supply for said main circuit, and acontrol device responsive to the current-flow in said main circuit.

8. The invention as defined in claim 1, characterized by said arcingdevice having a makealive electrode in continuous contact with one ofthe main electrodes for forming a cathode spot on the latter when themake-alive electrode is suitably energized, and means for suitablyenergizing said make-alive electrode after the control device hasaccomplished its principal purpose.

9'. The invention as defined in claim 3, characterized by said arcingdevice having a makealive electrode in continuous contact with one ofthe main electrodes for forming a cathode spot on the latter when themake-alive electrode is suitably energized, and means for suitablyenergizing said make-alive electrode after the relay has accomplishedits principal purpose.

10. The invention as defined in claim 5, characterized by said arcingdevice having a makealive electrode in continuous contact with one ofthe main electrodes for forming a cathode spot on the latter when themake-alive electrode is suitably energized, and means for suitablyenergizing said make-alive electrode after the control device hasaccomplished its principal purpose.

11. The invention as defined in claim 6, characterized by said arcingdevice having a makealive electrode in continuous contact with oneTHOMAS H. LONG.

